The long-term objective of this program is extended low-temperature preservation of organs. The emphasis of this proposal is in part on basic studies to further elucidate the mechanisms of freezing injury and of cryoperservation and, in part, on applied studies of kidney preservation. The basic studies are designed to explore the nature of cell injury from osmotic dehydration. In particular, we will test the hypothesis that the volume reduction which results from osmotic dehydration causes a reduction of cell surface tension which in turn leads to a loss of membrane stability with increase in membrane material. some specialized natural approaches to freezing tolerances will also be investigated, particularly a newly discovered mechanism in hardy poplar which apparently has evolved a tolerance to intracellular ice. The applied studies will be of three general categories. First, perfusion of rabbit and dog kidneys or kidney tissue with cryoprotectants to permit unfrozen storage at temperatures of the order of -8 degrees to -10 degrees C. Second, perfusion of kidneys with cryoprotectants to permit freezing to -80 degrees C or below. Third, the use of elevated hydrostatic pressure to permit low temperature storage without ice formation in the presence of feasible concentrations of cryoprotectant. All of these studies require the development both of perfusion regimens that do no osmotic damage and methods for circumventing the toxicity exhibited by cryoprotectants at high concentration. Hydrostatic pressures of the order of 1,000 atmospheres and above have been shown to cause cell damage and the interrelationships of pressure, temperature, cryoprotectants and exposure time will be explored. Vitrification would entirely obviate the problems associated with ice formation and is a promising new approach to low temperature preservation.